// Copyright 2017 The Cockroach Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// This software (KWDB) is licensed under Mulan PSL v2.
// You can use this software according to the terms and conditions of the Mulan PSL v2.
// You may obtain a copy of Mulan PSL v2 at:
//          http://license.coscl.org.cn/MulanPSL2
// THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
// EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
// MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
// See the Mulan PSL v2 for more details.

// +build !windows

package log

import (
	"os"

	"golang.org/x/sys/unix"
)

func dupFD(fd uintptr) (uintptr, error) {
	// Warning: failing to set FD_CLOEXEC causes the duplicated file descriptor
	// to leak into subprocesses created by exec.Command. If the file descriptor
	// is a pipe, these subprocesses will hold the pipe open (i.e., prevent
	// EOF), potentially beyond the lifetime of this process.
	//
	// This can break go test's timeouts. go test usually spawns a test process
	// with its stdin and stderr streams hooked up to pipes; if the test process
	// times out, it sends a SIGKILL and attempts to read stdin and stderr to
	// completion. If the test process has itself spawned long-lived
	// subprocesses that hold references to the stdin or stderr pipes, go test
	// will hang until the subprocesses exit, rather defeating the purpose of
	// a timeout.
	nfd, _, errno := unix.Syscall(unix.SYS_FCNTL, fd, unix.F_DUPFD_CLOEXEC, 0)
	if errno != 0 {
		return 0, errno
	}
	return nfd, nil
}

func redirectStderr(f *os.File) error {
	return unix.Dup2(int(f.Fd()), unix.Stderr)
}
